Methods and systems for client-side, on-disk caching

Abstract

A system and method for persistently caching data elements in the internal storage of a client connected to an enterprise network allows for the rapid access of data elements by the client. The persistent caching of data elements significantly reduces the number of times the client must request data elements from a remote storage area. The persistently cached data elements are further checked for coherency with the server at specified intervals to make certain that the cached copies are always coherent with the server when called by a client application.

1 . A method for caching data elements on a client coupled to a server, wherein the data elements originate on a database operatively connected to a server, the method comprising: 
 selecting at least one data element from a plurality of data elements stored on the database;    retrieving the selected at least one data element from the database;    storing a copy of the selected at least one data element on a storage device associated with the client;    defining a time period for which the copy is considered coherent; and    persisting the copy in the storage device for at least the time period.    
     
     
         2 . The method of  claim 1 , further including: 
 determining if the time period has expired, and    if the time period has expired, determining if the copy is coherent.    
     
     
         3 . The method of  claim 2 , wherein if the copy is determined to not be coherent: 
 deleting the copy from the storage device; and    re-retrieving the selected at least one data element from the database; and    storing a coherent copy of the selected at least one data element on the storage device.    
     
     
         4 . The method of  claim 1 , wherein selecting at least one data element further comprises: 
 selecting a plurality of data elements from the plurality of data elements stored on the database; and    forming a group of selected data elements, wherein the time period for copies of the selected data elements in the group stored on the storage device is the same.    
     
     
         5 . The method of  claim 4 , further including: 
 determining if the time period has expired, and    if the time period has expired, determining if at least one of the copies are coherent.    
     
     
         6 . The method of  claim 5 , wherein if the copies are not coherent: 
 deleting the copies from the storage device; and    re-retrieving the group of selected data elements; and    storing coherent copies on the storage device.    
     
     
         7 . The method of  claim 2 , wherein: 
 the copy is considered to be coherent if an associated property of the stored copy matches an associated property of the selected at least one data element stored on the database.    
     
     
         8 . The method of  claim 5 , wherein: 
 the copies are considered to be coherent if an associated property of at least one of the copies of the selected data elements stored on the storage device matches an associated property of at least one of the selected data elements stored on the database.    
     
     
         9 . A system for on-disk client-side caching comprising: 
 a client connected to a server through a network;    a database operatively connected to the server;    a central processing unit (CPU) in the client which: 
 selects at least one data element stored in the database to be stored on a client storage device;  
 retrieves the selected at least one data element and stores a copy of the selected at least one data element on the client storage device;  
 defines a time period for which the copy is considered coherent; and  
 persists the copy on the client storage device for at least the defined time period.  
   
     
     
         10 . The system of  claim 9 , wherein the CPU: 
 sends a request from the client to the server to determine if the copy is still coherent.    
     
     
         11 . The system of  claim 10  wherein the CPU: 
 deletes the copy from the client storage device and retrieves the selected at least one data element from the database, and stores a coherent copy of the selected at least one data element on the client storage device when the CPU determines that the copy is no longer coherent.    
     
     
         12 . The system of  claim 9 , wherein the CPU: 
 selects a plurality of data elements; and    forms a group of selected data elements wherein 
 the time period for copies of the selected data elements in the group stored on the client storage device is the same.  
   
     
     
         13 . The system of  claim 12 , wherein the CPU: 
 sends a single request from the client to the server to determine if at least one of the copies are still coherent.    
     
     
         14 . The system of  claim 13 , wherein the CPU: 
 deletes the copies from the client storage device and retrieves the group of selected data elements from the database and stores coherent copies of the selected data elements in the group on the client storage device when the CPU determines that at least one of the copies are no longer coherent.    
     
     
         15 . The system of  claim 9 , wherein: 
 the copy is coherent if an associated property of the stored copy matches an associated property of the selected at least one data element stored on the database.    
     
     
         16 . The system of  claim 13 , wherein: 
 the copies are considered coherent if an associated property of at least one of the copies of the selected data elements stored on the storage device matches an associated property of at least one of the selected data elements stored on the database.    
     
     
         17 . A method of on-disk, client-side caching of data elements, wherein the client is coupled to a server, the method comprising: 
 selecting at least one data element out of a plurality of data elements stored on a database operatively connected to the server to be cached;    defining a check period for the selected at least one data element;    retrieving the selected at least one data element from the database;    persistently storing a copy of the selected at least one data element in a client's on-disk cache, wherein 
 the copy is considered to be coherent with the database for at least the check period; and  
   determining whether the copy is coherent with the database when the check period expires, 
 wherein if the copy is determined to not be coherent, deleting the copy from the on-disk cache;  
 re-retrieving the selected at least one data element from the database; and  
 persistently storing a coherent copy of the selected at least one data element in the on-disk cache.  
   
     
     
         18 . A method of on-disk, client-side caching of data elements, wherein the client is coupled to a server, the method comprising: 
 selecting data elements to be cached;    defining a group of data elements comprising the selected data elements;    defining a check period for the group of data elements;    retrieving the group of data elements from the database;    persistently storing copies of the data elements in the group in a client's on-disk cache wherein 
 the copies are considered to be coherent with a database operatively connected to the server for at least the check period; and  
   determining whether the copies are coherent with the database when the check period expires, 
 wherein if the copies are determined to not be coherent, deleting the copies from the on-disk cache;  
 re-retrieving the group of data elements from the database; and  
 persistently storing coherent copies of the data elements in the group in the on-disk cache.